The industry has continued voluntary testing to supplement available environmental and toxicological information on MTBE.
1.3.1.2 Health risk reviews
The weight of scientific evidence shows that MTBE has a low order of acute and sub-acute toxicity. It is not mutagenic, neurotoxic, nor is it a reproductive toxicant.
The following is a summary of the health hazard and risk evaluations and reviews published by well-recognised research entities, scientific and regulatory bodies.
1) CONCAWE appendix no. 2.pdf is the European Oil Companies’ organisation (CONCAWE) publication no: 97/54, entitled “The health hazards and exposures associated with gasoline containing MTBE”. It contains a section (Chapter 5) on “Comparison of the Health Hazards of Gasoline and Gasoline/MTBE Blends” which compares health aspects of traditional and oxygenated gasolines. No significant difference could be found.
2) WHO (World Health Organisation) The WHO International Programme on Chemical Safety (IPCS) says that "based on collective evidence, it appears unlikely that MTBE alone induces adverse acute health effects in the general population under common exposure conditions." More information can be found on the IPCS website in the Environmental Health Criteria Document No. 206. http://www.inchem.org/documents/ehc/ehc/ehc206.htm
3) ECETOC Furthermore, a scientific task force in Europe, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) in Brussels examined the health risks associated with the use of MTBE and concluded that the risk characterisation for MTBE does not indicate concern for human health with regard to current occupations and consumer exposures.
The ECETOC Risk Assessment content List and Chapter 4.1.3, Risk Characterisation (on human health) can be found in appendix no. 3.pdf The full report, ECETOC Special report No.17 was published in December 2003.
4) EU-Risk Assessment MTBE has recently undergone a full health and environmental risk assessment according to EU-guidelines. The risk assessment was prepared on behalf of the EU-Commission by the Finnish Competent Authorities under review of Competent Authorities from European member States. Besides environmental effects all known health effects were evaluated, together with the potential for exposure, in order to assess the overall health risk that MTBE may present.
The EU Risk Assessment on MTBE was finalised in November 2001 and the conclusions were published in the Official Journal of the European Communities on 4th December 2001, see
http://europa.eu.int/eur-lex/pri/en/oj/dat/2001/l_319/l_31920011204en00300044.pdf.
The full Risk Assessment Report was published on September 20th, 2002 and is available on the ECB´s web page http://ecb.jrc.it/existing-chemicals/, click on ESIS, search for CAS# 1634-04-4, scroll down and view Final RAR, published in “European Risk Assessment Report Volume 19”.
5) RIVM In 2004 the Dutch Ministry of Housing, Spatial Planning and the Environment (VROM) ordered the national Research Institute RIVM to derive solid risk limits for soil, sediment, groundwater, surface water, drinking water and for drinking water preparation. When deriving this risk limits co-ordination with the Risk Assessment Report from the EU RA (2002) took place. The report (76 p. in Dutch, with a short English abstract) can be downloaded in PDF format (320 kB) from Www.rivm.nl/bibliotheek/rapporten/711701039.html
A literature summary of the human health effects of MTBE can be found at:
http://sd.water.usgs.gov/nawqa/vocns/mtbe_hh_summary.html
While a bit out of date and superseded by various other concluding studies (e.g. the European Risk Assessment, see par. 1.3.3), this literature review by the Oregon Health & Science University is still useful.
1.3.2 Research conclusions
1.3.2.1 Carcinogenicity
The possible carcinogenicity of MTBE was intensively discussed in the past. However several independent bodies in Europe and the United States concluded recently that MTBE is not a human carcinogen.
1) In 1998 the International Association of Research on Cancer (IARC) - a World Health Organisation agency composed of leading cancer researchers, scientists and health professionals - classified MTBE in Category 3 (“not classifiable as to its carcinogenicity to humans”). This means that despite the large number and high quality of research studies, there is no evidence to establish a possible cancer risk to man from exposure to MTBE. For reference, Category 3 also includes several large-volume everyday foodstuffs.
The IARC scale runs from 1 to 4. Substances in Group 1 are known to cause cancer in humans, those in Group 2A are probably carcinogenic, in Group 2B possibly carcinogenic and those in Group 4 are probably not carcinogenic. In this latter group, only one chemical (caprolactam) is classified. Gasoline is classified in Group 2B -- possible human carcinogen -- while benzene and alcoholic beverages are both classified in Group 1 -- known human carcinogens.
IARC data A Summary of Data Reported and Evaluation of IARC’s report is available via the following Internet link: http://www-cie.iarc.fr/htdocs/monographs/vol73/73-13.html For definition of Groups, see Preamble Evaluation on the same page.
2) In the U.S., the National Toxicology Program Executive Committee (NTP) (a multi-agency review panel comprising: Agency for Toxic Substances & Disease Registry, U.S. Consumer Product Safety Commission, U.S. EPA, Food & Drug Administration, National Center for Environmental Health, National Cancer Institute, National Institute of Environmental Health Sciences, National Institutes of Health, National Institute for Occupational Safety & Health, and the Occupational Safety & Health Administration) concluded that MTBE did not deserve to be listed as a ”known” or “reasonably anticipated” human carcinogen. MTBE is not listed in the current NTP carcinogenicity report about chemicals which are known to cause human cancer. (See following website http://ntp-server.niehs.nih.gov/index.cfm?objectid=72016262-BDB7-CEBA-FA60E922B18C2540, 10th report on carcinogens).
3) The State of California also concluded that MTBE is not a human carcinogen and does not cause birth defects or infertility. MTBE is not on the current list of chemicals meeting California’s Proposition 65 criteria for listing as “known to the state to cause cancer or reproductive toxicity”. Further information can be found on: www.oehha.ca.gov/prop65.html (go to “current list of chemicals”).
4) Furthermore, a scientific task force in Europe, examining the health risks associated with the use of MTBE concluded that, “MTBE is not carcinogenic according to the criteria set forth in the European Union’s Directive on Dangerous Substances.” The European Centre for Eco-toxicology and Toxicology of Chemicals (ECETOC) also concluded, “the risk characterisation for MTBE does not indicate concern for human health with regard to current occupations and consumer exposures.”
The ECETOC Risk Assessment’s (see chapter 1.3.1.2, item 3)
5) The rapporteur for the EU MTBE Risk Assessment, i.e. the National Product Control Agency for Welfare and Health, Chemicals Department, Finland and the Finnish Environmental Institute has announced in a press release (December 8th, 2000) that based on the assessment work performed in various scientific working groups, it will not suggest a carcinogenicity classification for MTBE. The EU-Commission has recently published official classification and labelling for MTBE in the Directive 2004/73/EEC from April 2004. MTBE is classified as an irritant and highly flammable substance only.
More information under
http://europa.eu.int/eur-lex/pri/en/oj/dat/2004/l_152/l_15220040430en00010311.pdf see Index No. 603-181-00-X
1.3.3 EU Risk Assessment
1.3.3.1 Introduction
MTBE has undergone an EU full health and environmental risk assessment. In 1997, MTBE was included in the third Priority List of substances selected for risk assessment under Council Regulation (EEC) 793/93 on the evaluation and control of the risk of existing substances. Finland was chosen as the Member State “Rapporteur” responsible for progressing the risk assessment on MTBE on behalf of the European Commission.
In the assessment process, all known health and environmental effects are evaluated, together with the potential for exposure, in order to assess the overall risk that a substance may present. The process includes a review of the appropriate classification and labelling of the substance.
The EU Risk Assessment on MTBE was finalised in November 2001 and the conclusions including risk reduction strategy were published in the Official Journal of the European Communities on 4th December 2001. The Risk Assessment Report was published on September 20th, 2002 as a hard copy and at ECB´s web page http://ecb.jrc.it/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/REPORT/mtbereport313.pdf
1.3.3.2. Summary of findings
After considering all the available information, the EU Rapporteur concluded that:
Exposure to MTBE was not expected to have any harmful impact on human health, the atmosphere or the environment. However risk reduction measures are necessary to protect ground water quality by introducing European minimum standards for technical equipment for MTBE use, especially for storing equipment. In many EU member states according regulations are already in force.
In the risk assessment report in 2002 it was mentioned that additional information is needed to characterise possible risk to the aquatic ecosystem regarding to the emission to surface water. Tests regarding tainting of fish by MTBE and avoidance of fish against water with MTBE impurities have since been conducted and an addendum to the risk assessment report was published in 2004. It concluded that neither fish tainting nor fish avoidance behaviour is occurring at a concentration of 15 µg/l which is far above typical MTBE concentration in surface water. The addendum is also available on the same website as the full report, see above.
1.3.4 Other health effects
Acute health effects from exposure to MTBE have also been considered and addressed in a number of studies.
In 1995, the World Health Organisation concluded that it is "unlikely that MTBE alone induces adverse acute health effects in the general population under common exposure conditions."
The strong taste and odour of MTBE mean that, even at very low concentrations, its presence makes drinking water unpalatable. The US EPA has recommended an MTBE concentration in drinking water of 20 to 40 ppb or below. These levels preserve the palatability of drinking water and are 20,000 to 100,000 times lower than the lowest concentration that has caused observable health effects in animals.
Note, the taste and odour of MTBE are not a health problem but an issue of water quality.
